i'm planning to build rwd mid-engined buggy around honda engine and subaru transmission. Thanks to japan used cars market there is plenty of inexpensive parts to choose from.
I already have 300Nm/250hp engine and now I'm looking for a manual gearbox from fwd subaru.

Make transmission coupling plate and find suitable gear ratios is not a problem for me, but I have very little knowlege about differentials.

Obviously open diff is not the best choice. Nor the welded one.

So here's the question: what/which one is better for a rear-drive vehicle on non-tarmac surfaces (mud, gravel, snow etc.)?

Should I buy a gearbox with built-in LSD of some kind, or it will be better to buy the diff unit separately and install it into gearbox?